Chapter 9: Amino Acids and Proteins Flashcards
Isoelectric point (pI)
The pH at which the amino acid or protein has no net charge and the positive charges equal the negative charges
pH > pI: negative charge
pH < pI: positive charge
Primary structure
The sequence of amino acids in the polypeptide chain
Secondary structure
Determined by the interaction of adjacent amino acids (alpha helix, beta pleated sheets, random coils)
Tertiary structure
The way in which the chain folds back upon itself to form a 3-dimensional structure
Quaternary structure
The arrangement of two or more polypeptide chains to form a protein
Denaturation
The disruption of the bonds holding the structures together; can occur as a result of heat, changes in pH, mechanical forces, UV exposure, and chemical exposure
Alkaptonuria
Disease involving the homogentisic acid oxidase (HGO) that leads to a buildup of homogentisic acid (HGA) in the tissues of the body; leads to ochronosis which is the darkening of the body tissues
Cystinuria
Cystine is somewhat insoluble, leading to precipitation in renal tubules (forms urinary calculi)
Maple syrup urine disease
Caused by the absence or very low levels of alpha ketoacid decarboxylase; results in the abnormal metabolism of leucine, isoleucine, and valine
Phenylketonuria (PKU)
Results in the inability to metabolize phenylalanine; elevated levels of phenylalanine are toxic to developing brain tissue and negatively impact brain function
Proteins are categorized into two main groups
Albumin, Globulin (a1 globulins, a2 globulins, B1 globulins, Y globulins)
Prealbumin/Transthyretin
Main clinical significance of prealbumin is its role as a sensitive marker of poor nutritional status
Albumin
Comprises ~60% of the total serum protein; chief biological function is to maintain plasma colloidal osmotic pressure (COP) and to transport/store a wide variety of ligands
Hypoalbuminemia
Decreased albumin levels; most common cause is increased catabolism due to tissue damage and inflammation
